1. Field of the Invention
The present invention relates to an apparatus and method for recharging a battery.
2. Description of Related Art
A battery may be recharged by applying power to the device for a period of time. There have been developed various methods for applying power to recharge a battery. One method is to provide a continuous charging current that induces a change in the chemical composition of the battery. Such a method requires a relatively large charging current which tends to overheat and warp the battery plates. Additionally, it is has been found that a DC charge will not always fully restore the battery.
U.S. Pat. No. 4,740,739 issued to Quammen et al. discloses a method for charging a battery which includes the step of periodically allowing the battery to discharge during the charging process. In the Quammen method a continuous charging current is applied to the battery. The Quammen charging apparatus includes a pulse train generator and an electronic switch that are coupled to the battery. The pulse train generator periodically drives the switch so that a discharge current flows from the battery. The pulse train generator drives the switch every 600 to 1200 microseconds.
U.S. Pat. Nos. 4,871,959; 5,084,664 and 5,276,393 issued to Gali disclose a solar powered battery charger. The Gali battery chargers include a DC to AC converter which applies a pulsed current to the battery. The '393 patent discloses a waveform applied to the battery that is a series of very sharp pulses provided at a frequency between 10,000 and 100,000 hertz. The pulses have a rise time of less than 100 nanoseconds. Gali claims that this series of short pulses will generate a ringing signal in the battery that matches the resonant frequency of the battery. Gali further claims that the battery can be recharged with such pulses without providing a continuous charging current to the device. The low power requirements allow Gali to utilize a solar conversion energy source.
U.S. Pat. No. 5,648,714 issued to Eryou et al. discloses a battery recharger which utilizes a transistor switch and an inductor to introduce a series of short pulses in a DC current that is used to charge a battery. The repetitive rate of the pulses appears to be less than 2500 hertz.
It has been found that the recharging methods of the prior art are not always successful in fully restoring a depleted battery. It would be desirable to provide an apparatus and method for fully restoring any battery.